The broad objective of this project is the elucidation of the etiology and pathogenesis of sarcoidosis so that a soundly based program of prevention and therapy can be established for this widespread systemic disorder. The hub of the project is the systematic effort to purify, isolate and characterize by currently available chemical, physical, isotopic and immunologic techniques, the active components(s) in human sarcoidal tissues which are responsible for eliciting specifically a positive intracutaneous Kveim reaction in subjects with sarcoidosis. It is hoped that characterization of these Kveim components will help illuminate the nature of the active granulomagenic principle in Kveim suspensions. With a knowledge of the nature of this active principle it may be possible to devise an effective in-vitro Kveim test as well as an appropriate animal model to help define more precisely the immunologic determinants of granuloma formation which may prove applicable, as well as, to other granulomatous disorders such as Crohn's disease, leprosy, beryllium disease, etc.